JPH0768886B2 - Steam turbine, device for preventing axial movement of disc, and disc mounting method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to rotors for turbomachines such as steam turbines. More particularly, the present invention relates to apparatus and methods for inhibiting axial movement of discs or disks shrink-fitted to a steam turbine rotor shaft.

[0002] Steam turbine rotors typically include a shaft having a plurality of vanes or blades fixed at the periphery. The shaft also comprises a disc called a "dummy" disc that has no vanes formed. In one configuration example, this dummy disk has an interference fit and radial pin (centering pin) near the disk surface on the downstream side.
It is shrink-fitted and fixed to the shaft so as to be held by. The dummy disk induces in the rotor an axial force that acts to balance the thrust exerted on the rotor by the steam expanding through the blade row. As a result of the differential thermal expansion between the disc and the shaft and the centrifugal forces acting on the disc, the effect of the interference fit holding the disc on the shaft is reduced during operation. Then, with temperature, the disk tends to extend upstream from the radial pin. Further, since the disk surface on the downstream side is hotter than the disk surface on the upstream side, the disk has an umbrella shape, so that the interference fit becomes stronger on the disk surface side on the upstream side. Upon shutdown, the disk thermally contracts, thereby tending to exert a pulling force on the pin while adhering to the rotor at the upstream disk surface. As a result, the dummy disk tends to ratchet along the axis during the start-stop cycle. Such axial movement of the disk can result in the disk interfering with stationary components that are fixed to the steam turbine casing.

Conventionally, radial retaining or radial pins mounted through holes formed in the dummy disk and shaft are used to prevent axial movement of the dummy disk along the axis. It had been. However, these pins are not completely satisfactory in constraining the disc, and studies have shown that in some rotors, dummy discs have 0.150 cm (0.060 cm).
Inch) has also been found to move axially. Such axial movement is accompanied by significant deformation of the radial pin, which lacks sufficient shear area to resist the axial forces tending to move the disc. It is shown that.

Therefore, it would be desirable to develop a device having a shear cross section of sufficient magnitude to prevent axial movement of the shrink-fitted disc along the axis.
In addition, using such equipment, existing steam turbine
It would be desirable to provide a method of retrofitting or retrofitting a rotor. Furthermore, since it is believed that differential motion between the disc and rotor on the upstream face of the disc must be eliminated to prevent the above-mentioned ratchet-like movement of the disc, the upstream face It is desirable to fix the disc with.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method and apparatus for inhibiting axial movement of a disc along its axis.

Another object of the present invention is to provide such a device having sufficient shear cross-section to resist large axial forces without significantly weakening or increasing the working stress in the disk. It is in.

Yet another object of the present invention is to provide a device for fixing a disc on its upstream side surface.

Yet another object of the present invention is to provide a method of retrofitting an existing steam turbine using the apparatus without significantly exceeding the envelope of the existing rotor.

The above and other objects are accomplished in a steam turbine having a casing containing a plurality of fixed vanes and a shaft surrounded by the casing.
A first groove extending in the circumferential direction is formed in the peripheral portion of the shaft. A disk with a hub surrounds the shaft near this first groove. A groove extending in the second circumferential direction is formed in the hub. A plurality of arcuate retaining members, each having first and second retaining portions, are used to prevent axial movement of the disc relative to the shaft. The second holding portion of each holding member extends in the axial direction and is arranged in the second groove. Further, the first holding portion extends inward in the radial direction from the second holding portion and is arranged in the first groove.

A holding member inlet slot is formed in the second groove, and the combined radial height of the inlet slot and the second groove is at least equal to the radial height of each holding member. It is about the size. A closure member is disposed in the inlet slot to prevent circumferential movement of the retaining member within the first and second grooves. The at least one holding member is a locking or fixing holding member and is arranged inside the inlet slot, that is, radially inward of the inlet slot, and the second holding portion of the locking holding member and the closing member. The combined radial height of the inlet slot and the second
Is substantially equal to the combined radial height of the grooves. A screw hole (a screwed hole) is formed between the closing member and the locking holding member, and a first portion of the circumference of the screw hole is formed in the closing member, and a first portion of the circumference of the screw hole is formed. The second portion is formed on the lock holding member. An axially oriented locking screw is threaded into the threaded hole to prevent axial movement of the closure member and secure the closure member to the locking retaining member.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENT A high pressure steam turbine 1 is shown in FIG.
FIG. The main components of the steam turbine 1 are a fixed casing assembly 2 and a centrally located rotor 3 enclosed within the casing assembly 2. The casing assembly 2 is composed of a plurality of blade rings 4 fixed to the casing assembly and a plurality of fixed blades 5 fixed to each of the blade rings 4. The rotor 3 is provided with a shaft 8 on which a plurality of grooves 7 are cut. A plurality of rotary blades 6 are arranged in each of these grooves 7. The high pressure steam 35 flows into the high pressure steam turbine 1 via an inlet 37 formed in the casing assembly 2. After passing through each of the stages including the plurality of rotary vanes 6 and the fixed blades 5, respectively, the steam 36 is
The reduced pressure exits the high pressure steam turbine 1 via an outlet 38 formed in the casing assembly 2.

As best shown in FIG. 2, a dummy disk 9 is shrink fit onto the shaft 8. A ring 21 attached to the casing assembly 2 forms a front cavity 11 and a rear cavity 12 around the dummy disk 9. The steam supply system (not shown) for these cavities is
The rear cavity 12 is configured to be supplied with steam at a higher pressure than the front cavity 11. As a result of the pressure difference between the cavities 11 and 12, a net axial force acting upstream is induced in the dummy disk 9. This axial force tends to offset the thrust load acting on the rotor 3 and acting downstream as a result of the steam pressure decreasing as it flows through the turbine.
In this way, the dummy disk 9 functions as a thrust balancing device. Communication between the cavities 11 and 12 is prohibited by a seal 23 held by the ring 21 and surrounding the dummy disk 9.

As shown in FIG. 2, a boss or hub 10 is formed on the inner surface of the dummy disk 9. When first cut, the inner diameter of the hub 10 is smaller than the outer diameter of the outer surface 14 of the shaft 8 which it surrounds. Therefore, when the dummy disk 9 is shrink-fitted on the shaft 8, the dummy disk 9 is held on the shaft 8 by an interference fit. As already mentioned, this interference fit is not sufficient to prevent the gradual axial movement of the dummy disk 9 in the upstream direction along the axis 8. According to the present invention, this upstream movement is blocked by a plurality of arcuate holding members 15, as will be described later.

As shown in FIGS. 3 and 4, a groove 17 extending in the circumferential direction is formed in a region of the surface 22 extending in the radial direction on the upstream side of the dummy disk 9 and intersecting with the hub 10.
A groove 16 extending in the second circumferential direction is formed on the outer surface 14 of the shaft 8. Grooves 16 and 17 are grooves 16 and 17
Are axially aligned such that their downstream radially extending walls 25 and 26 lie in the same radially extending plane. A plurality of holding members 15 are arranged in the grooves 16 and 17. As shown in FIG. 3, each holding member 15 is an arc-shaped member. As shown in FIG. 4, each holding member includes a holding portion 19 that extends substantially in the axial direction and a holding portion 20 that extends substantially in the radial direction. “L-shaped” and has the holding portions 19 and 2
0 forms the "L-shaped" first and second legs. The holding part 19 is arranged in the groove 17 of the dummy disk 9, and the holding part 20 is arranged in the groove 16 formed in the shaft. Therefore, the upstream axial movement of the dummy disc 9 causes the wall 26 of the disc 9 to abut against the retaining part 20 of the retaining member 15, while this retaining part 20 of the retaining member 15 causes the wall 27 of the groove 16 of the shaft 8 to move. Is blocked by abutting against.

The grooves 16 and 17 in the preferred embodiment are
Each surrounds the disc 9 and the shaft 8 and extends over 360 °. As shown in FIG. 3, each holding member 15 occupies a relatively small arc portion. Therefore, the combined circular arc surrounded by all the holding members has a groove 16 of 360 °.
And a sufficient amount of the holding member 15 so as to fill the whole
Will be used. Therefore, all holding parts 20
The composite shear cross section of is sufficient to withstand very large axial forces.

As shown in FIGS. 3 and 5, the local portion of the groove 17 is radially expanded to form an inlet slot 18. The combined radial height of the inlet slot 18 and the groove 17 is at least the radial direction of the retaining member 15 so that the retaining member can be axially inserted into the groove 17 via the inlet slot. It is about the same size as the height of. The last holding member 1 installed in the grooves 16 and 17
Reference numeral 5 is a special locking or fixing holding member 24, as best shown in FIG. The locking holding member 24 has two screw hole portions 2 as described later in detail.
It is the same as the other holding members 15 except that 8 is added. Within the inlet slot 18 is a locking retaining member 2
4, a closing member 30 is arranged outside the holding member 24 in the radial direction. The radial thickness of the closure member 30 is such that the closure member 30 fits snugly within the inlet slot 18 and between the outer surface 14 of the shaft and the outwardly facing surface defining the inlet slot 18. Are selected so that substantially no gap is created.

As shown in FIG. 7, two screw holes 3
The circumferential half 29 at 4 is formed on the inward surface of the closure member 30. As shown in FIG. 8, the other half portion 28 of the circumference of the screw hole 34 is formed on the outer surface of the lock holding member 24. As shown in FIG. 5, the two halves 2 that define the screw hole.
Since 8 and 29 are circumferentially aligned, the closure member 3
When the 0 is placed in the inlet slot 18, the inward surface of the closure member coincides with the outer surface of the locking retaining member 24 and the two screw hole halves 28 and the two screw hole halves 29 combine. Two complete axially oriented screw holes 34 are formed.

As shown in FIGS. 5 and 6, an axially oriented locking screw 31 is screwed into each hole 34, whereby the closing member 30 is fixed to the locking holding member 24. In this way, the lock holding member 24
The closing member 30 is moved axially so that the inlet slot 1
8, and the closure member prevents the locking retaining member from moving radially and circumferentially in the grooves 16 and 17. As already mentioned, the holding members 15 and 24 fill the entire space of the grooves 16 and 17 over 360 °, so that locking or fixing the locking holding member 24 in place in the circumferential direction is not possible. All of the holding members 15 are also locked or fixed at predetermined positions in the circumferential direction. With this configuration, reliable locking or fixing by the locking screw can be realized without introducing stress concentration related to the screw hole to either the shaft 8 or the disk 9 which is a member subjected to high stress.

As shown in FIGS. 5 and 6, the screw 31 is
The pants-shaped washers 32 held by the screws are fixed in place so as not to rotate. This pants-shaped washer is shown in FIG. In order to clarify the illustration,
In FIG. 6, the tab 33 on one end of the pant-shaped washer 32 is shown in the form observed when the washer is first installed, while the tab on the other end of the washer is the side of the hexagonal head of the screw 31. Is shown as observed after bending around. However, the tabs 33 on both ends of the pant-shaped washer 32 are both folded around the head of the screw 31 so that the two screws 31 are retained.

The present invention is, for example, for heating the disk 9 and the shaft 8.
It is possible to carry out this by simultaneously removing the dummy disk 9 from the shaft 8 by expansion and then refurbishing the rotor 3 in that state.
Therefore, the groove 16 is cut on the outer surface 14 of the shaft 8. Next, the dummy disk 9 is shrink-fitted onto the shaft 8 by again heating the disk 9 and cooling the shaft 8 at the same time, for example.
7 and inlet slot 18 to hub 1 on surface 22 of disk 9
It cuts to 0 points. Alternatively, the groove 17 and the inlet slot 18 could be cut in the disk 9 before the disk 8 was shrink-fitted onto the shaft 8.

When the cutting is complete, the retaining members 15 are inserted one at a time into the inlet slots 18 and slid along the grooves 16 and 17. Once the grooves 16,17 have been filled with the retaining member 15 except for the portion inside the inlet slot 18, the locking retaining member 24 is inserted into the inlet slot and then the closing member 30 is inserted. As such, a hole 34 is drilled between the closure member 30 and the locking retaining member 24 such that the centerline of the hole 34 is located at the intersection of the mating surfaces of the closure member 30 and the locking retaining member 24. To do. Next, the hole 34 is tapped. Alternatively, the closure member 3
0 and the lock holding member 24 are installed as described above,
The holes 34 could be drilled and tapped, for example, by fastening the closure member to the locking retaining member with a vise.

After the closing member 30 and the lock holding member 24 are installed at the predetermined positions, the pants-shaped washer 32 is applied to the radial surfaces of the closing member and the lock holding member, and the locking screw 31 is placed in the hole 34. To secure the closure member to the locking retaining member and to secure the pant-shaped washer. After tightening the lock screw 31,
The tab 33 of the pant-shaped washer 32 is folded around the side of the hexagonal head of the locking screw, as shown at one end of the pant-shaped washer 32 in FIG.

Although the screw 31 is shown as a locking fixture or means for locking, it will be apparent to those skilled in the art that many other such as pin, snap ring, tongue and groove construction or welding, for example. The method can be used for locking fixation. Furthermore, although the present invention has been described with reference to the case where it is applied to a dummy disk in a steam turbine, the present invention also applies to vane steam turbine disks that are not integral with a shaft, compressors, pumps and gas turbines. It should be understood that it is equally applicable to discs in other types of turbomachines as well. Further, the groove 16
Although 17 and 17 have been described as extending through the disk 9 and the shaft 8 through 360 °, grooves enclosing smaller arc portions are also available. Thus, the present invention
It should be noted that the present invention can be embodied in other specific forms without departing from the spirit or essential attributes of the present invention, and thus the present invention is not limited to the embodiments described herein.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a high-pressure steam turbine.

2 is a detailed view of a portion of the steam turbine shown by rectangle II in FIG. 1. FIG.

FIG. 3 is a sectional view taken along line III-III in FIG.

FIG. 4 is a sectional view taken along line IV-IV in FIG.

5 is a cross-sectional view taken along the line VV in FIG.

FIG. 6 is a view taken along line VI-VI in FIG.

7 is a perspective view of the closing member shown in FIG.

8 is a perspective view of the lock holding member shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Steam turbine 2 Caging assembly 3 Rotor 8 Shaft 9 Dummy disk 10 Dummy disk hub 15 Arc-shaped holding member 16 First groove 17 Second groove 18 Inlet slot 19 Second holding portion of arc-shaped holding member 20 1st holding | maintenance part of an arc-shaped holding member 24 Holding member 31 for locking 31 Screw for locking 30 Closing member

Front Page Continuation (72) Inventor Lowell Mason Swarts Ringwood Drive, Winter Springs, Florida, USA 253

Claims (3)

[Claims] 1. In a steam turbine, a) a shaft having a first groove formed in a peripheral portion and extending in a circumferential direction; and b) a hub surrounding the shaft in the vicinity of the first groove and the hub. A disk having a second groove extending in the circumferential direction, and c) an arcuate holding member for preventing axial movement of the disk with respect to the shaft, the first groove A steam turbine comprising: a retaining member having a first retaining portion disposed therein and a second retaining portion disposed within the second groove. 2. A rotor having an axis and a disk, the disk having a radially extending surface, and a hub intersecting the surface and surrounding the axis, the rotor having a surface along the axis. A device for inhibiting axial movement of the disc, comprising: a) a first circumferentially extending peripheral portion of the shaft.
B) a second groove formed in the disk adjacent to the intersection of the hub and the surface and extending circumferentially; c) a first groove disposed in the first groove. Substantially L having a second leg and a second leg disposed in the second groove.
A disk axial motion restraint device comprising a V-shaped retaining member, and d) a first axially oriented locking screw extending into said second groove. 3. A rotor for a turbomachine having a shaft and a disk, the disk having a radially extending surface and a hub surrounding the shaft, wherein the disk is attached to the shaft. A) a first groove circumferentially extending around the shaft is machined; and b) a second groove circumferentially extending adjacent to the hub on the surface of the disc. C) machining an inlet slot in the face of the disc adjacent the second groove, d) shrink fitting the hub of the disc onto the shaft, and e) first and second. A plurality of arcuate holding members having two holding portions are arranged such that the first holding portion is arranged in the first groove and the second holding portion is arranged in the second groove. Insert into the inlet slot at: f) along the first and second grooves A method of mounting a disk in a turbomachine, comprising the steps of sliding each of the holding members to fill the circumferentially extending regions of the first and second grooves with the holding members.